The present invention relates to a magneto-optical recording medium such as a magneto-optical disc where data bits are recorded in the form of magnetic domains by a magneto-optical (thermal) recording process, and the recorded data bits are read out in accordance with the Kerr rotation angle or Faraday rotation angle based on the rotation of the polarization plane of the data read light.
There are known magneto-optical recording media as disclosed in, for example, Japanese Patent Laid-open NO. 57 (1982)-78652, wherein a double layer structure is contrived for the purpose of accomplishing a high reproduction capability and a high recording sensitivity, with a first magnetic film having a high Curie point and a small coercive force to serve as a reproducing magnetic film, and a second magnetic film magnetically coupled thereto and having a low Curie point and a great coercive force.
In the magneto-optical recording medium of such a double layer structure, the layer used for recording or erasing data is the reproducing magnetic film (first magnetic film), and a recording or erasing operation is performed at a temperature below the Curie point thereof. Consequently the magnetization of the first magnetic film in the recording operation is relatively great, and therefore the stray magnetic field and demagnetizing field resulting therefrom are also great in intensity. Thus, in the recording or erasure, it becomes necessary to apply an external magnetic field having a sufficient intensity of, e.g. 500 (oe) for completely canceling such stray magnetic field and demagnetizing field. Accordingly, there exists a problem that the above recording medium is not suited for overwriting which writes new data over the previously recorded data, by using an external magnetic field modulated according to a signal to be recorded.